Control device



Dec. 2, 1952 B. 1... JOHNSON 2,620,413

CONTROL DEVICE Filed July 6, 1948 .INVENTOR. BERTIL L. JOHNSON A TTOR/VE Y Patented Dec. 2, 1952 UNITED STATES PATENT OFFICE CQNTRGL DEVICE Eertil L. Johnson, Chaska, Minn, assignor to Minneapolis-Honeywell Regulator Company, Minneapolis, Minn, a. corporation of Delaware Appiication July 6, 1948, Serial No.'37,273

2 Claims. 1

This invention relates to condition responsive control devices and more particularly to means for adjusting such devices to operate at desired condition values.

One object of the invention is to provide a condition responsive control device in which the cut-in and cut-out points may be relatively varied.

Another object is to provide a device in which a snap switch is actuated in response to changes in variable condition and having two springs that may be adjusted to determine the condition values at which the switch is opened and closed.

A more specific object is to provide a pressure actuated switch in which the pressure is opposed by different springs or combination of springs when the switch is moved to closed and t open positions.

Other objects will be apparent from the detailed specification and claims, and from the drawing in which,

Figure 1 is an elevation, partly in section, of a pressure actuated switching device.

Figure 2 is a fragmentary sectional view taken on line 22 of Figure 1,

Figure 3 is a fragmentary view illustrating a modified form of the invention, and

Figure 4 is an elevation, partly in section, illustrating another modified form of the invention.

The pressure switch illustrated in Figure 1 is provided with a frame It that includes a base plate II. The plate II has a cup-shaped portion I2 formed therein which serves as the rigid element of a pressure responsive chamber. A thin cup-shaped metal diaphragm I3 is secured over the top of the cup-shaped portion [2 of the plate I l and serves as the movable element of a pressure chamber. An internally threaded pressure connection it is attached to the underside of the pressure chamber. The frame It also includes a bracket ll to which is secured a snap switch I8 having the usual push button type of actuator i Q. Snap switch 18 may be of the type disclosed in the patent to Albert E. Baak, 2,318,734, but the only requirement of this switch as far as the present disclosure is concerned is that the switch be operated to one of its operative positions at one position of the button is and to the other of its operative positions at a different position of the button [9.

The upper surface of the diaphragm 23 engages a plate 21 having upwardly extending projections 22 that engage a switch actuating lever 24. The lever 24 is pivoted on a pin 25 of the frame bracket [1. A spring strip 2! has its right-hand '2? end secured to the lever 24 adjacent the pivot 25 and its left-hand end engages the under side of the head of a screw .28 which is adjustably secured in the lever 24. An intermediate portion of the strip 21 is adapted to engage the switch actuating button 19. By adjusting the screw 23 it is possible to determine the position of the diaphragm I3 at which thespring strip 21 will actuate the switch. Also, on excessive pressure the strip 21 is adapted to leave the head of the screw 28 to act as a strain release. Upward movement of the lever 24 is resisted by a pair of springs as will be hereinafter described. An increase in pressure will raise the lever 24 and the spring strip 2! to actuate the switch in one direction. Likewise, a decrease in pressure will result in the lever '24 being moved downwardly to actuate the switch in the opposite direction.

A post 30 is adjustably mounted in the frame IE] by a screw-threaded portion 3i and is secured by a lock-nut 32. The post 39 carries a main spring 34 and a pick-up spring 35 both of which are adapted to oppose upward movement of the lever 24. The lower end of the spring 34 is carried by a spring retaining cup 3t which has a centrally located aperture to accommodate the post 33. The left-hand end of the lever 24 engases the under side of the cup 36. On variations in pressure the lever 24 raises and lowers the cup 35 on the post 39 to position the lower end of the spring 34. A nut 3'! which is screw-threaded on the upper end of the post 30 serves to adjustably position the spring retaining cup 58 to determine the position of the upper end of the spring 3 5. By adjusting the nut 3? it is possible to adjust the force exerted by the spring 34 on the lever 24 when the strip 27 engages pin is to actuate'switch I8.

The pick-up spring 35 is confined between spring retaining cups 40 and 4!. Downward movement of the lower cup 40 is limited by a shoulder 43 on the post 30. The position of the upper cup 4| is determined by an I-shaped member 45 that is located in a slot in the post 39. See Figure 2. The position of the member 45 and therefore the position of the upper end of the spring35 is determined by a nut 46 which is in threaded engagement with the post 36. It will be seen that the member 45 has its central portion extending through the central apertures in the nut 31 and the spring retaining cup 33. The member 45 may be assembled to pass through the nut 31 and cup 33 prior to assembly on the post 30. This is accomplished by bending one or more of the laterally extending ears of the member 45.

The post is adjusted in the frame it and the screw 28 is adjusted in the lever 24 to position the strip 27 relative to the lever 24 so that when the spring retaining cup 36 engages the retaining cup 50, the switch actuating button I9 will be intermediate the positions at which the switch is actuated to its two operative positions. When the pressure is increased and the lever 26 is moved upwardly from the position shown in Figure 1, the switch will not be actuated from its original position until the lever 24, through the cup 38, has raised the cup ti! and the lower end of the spring from the position shown. Thus, the pressure must overcome the forces of both the springs 34 and 35 before the switch will be actuated. On the other hand, when the pressure is reduced the switch will not be actuated to its original position until the lever 24 has lowered the spring retaining cup 36 to a position out of engagement with the cup GB, and hence only the force of the spring St has any effect on the pressure at which the switch is will be actuated to its original position.

The spring 35 may thus be adjusted. to vary both the cut-in and cut-out pressures of the switch, whereas the pick-up spring 35 may be adjusted to determine the operating differential of the switch. By providing a mechanism in which the difierential adjusting or pick-up spring 35 is located concentrically and inside the spring 34, a very compact structure is provided and one in which the parts are reduced to a minimum.

The bracket I! may be provided with an extension 49 on which suitable indicia may be placed to indicate the pressure settings of the spring 3%. Or, alternatively, the extension 48 may merely contain a suitable legend indicating the direction in which the nut 37 should be moved to raise or lower the control pressure.

Figure 3 shows a modification of the spring arrangement that difiers in some respects from that shown in Figure 1. It will be understood that the pressure chamber, switch and mechanical linkage may be the same as shown in Figure 1. A post 58 is secured to the plate ll of the frame [0 and carries a main spring 53 and a pick-up spring 54 concentrically thereon. The spring 53 is provided with retaining cups 55 and 55, the former of which is adapted to be engaged by the switch actuating lever 24. extension 5? which is also screw-threaded to carry a nut 58 which serves as an adjustable abutment for the upper spring retaining cup 55. The inner spring 54 bears against a spring retaining cup 60 Which is adapted to engage a shoulder 6| on the post to determine its lower limit of travel. The upper end of the spring 54 engages a cup 63 which is adjustably positioned by a shoulder 64 formed by the bottom end of the extension 5'! of the post 59. A collar 66 is slidable on the post 50 to transmit movement from the lower spring retaining cup to the cup which supports the lower end of the spring 5 3.

With the lever 24' in the position shown and the spring retaining cup 60 in engagement with the shoulder 6 I, the switch is intermediate its two operative positions. If the switch has not yet been actuated in the direction caused by pressure increase, it will be necessary to raise the lever 2% against a combined force of the springs 53 and 54 in order to actuate the switch. On the other hand, if the switch has not yet been actuated in a direction corresponding to a decrease in pressure, then the lever 2d will be lowered to actuate the switch only when the pressure is re- The post 55 has an duced to a value at which the force of the spring 53, acting along, will balance the pressure.

To adjust the pressure at which the switch will be actuated. on pressure increase the post extension 51 is rotated on the post 513 to determine the position of the upper end of the spring 54, and the nut 58 is adjusted on the post extension 51 to determine the position of the upper end of the spring 53. This pressure value depends on the adjustment of both springs. To select the pressure value at which the switch will be actuated on pressure decrease, only the spring 53 need be adjusted by rotating the nut 58 on the extension 51. This modification is similar to that shown in Figure 1 with the exception of the mechanism by which the inner and outer springs are adjusted.

Figure 4 shows another spring arrangement, and one in which the cut-in and cut-out values may be independently adjusted. Here also the pressure chamber, mechanical linkage and switch may be identical to the arrangement shown in Figure 1 and their description will not be repeated. A post 10 is suitably secured to the plate H and carries springs 12 and i3 concentrically with respect thereto. The lower spring 72 is confined between a lower retaining cup 15 and an upper retaining cup 76. The cup 76 is adjustable on a sleeve 18, which is axially slidable on the post 10, by a nut 79. The lower end of the sleeve 78 is limited in downward movement by a shoulder 8| on the post Hi. The lower cup engages the bottom of the sleeve 18 when it is raised upwardly by the lever 24 in response to pressure increase.

The lower end of the spring 13 is confined by a cup 82 and is positioned by the upper end of the sleeve 18. A nut 84 is adjustable on the post H3 to position a cup 85 to adjust the upper end of the spring 13.

It is necessary to move the lever 2 above the position in which the cup 15 engages the sleeve '18 in order to actuate the switch to one of its operative positions and it is likewise necessary to lower the lever 24 below that position to move the switch to the other operative position. As the pressure increases from the position shown in Figure 4 the lever 24 will be raised to compress the spring 12 to the extent permitted by the sleeve 18, but no switching operation will take place. When the lever 24 is raised above this position spring 12 is not further compressed, but rather the sleeve 18 together with the spring 72 are raised on the post Hi. The pressure required to cause this movement is determined solely by the spring 13, and hence the pressure value at which the switch is actuated in response to pressure increase is determined solely by adjustment of the nut 84 which determines the position of the upper end of the spring 13.

If the pressure is reduced, the lever 24 will lower the sleeve '18 until the sleeve abuts the shoulder 81, rendering the spring 13 inoperative.

To cause switch actuation it is then necessary to further reduce the pressure until the spring 72 overcomes the upward force on the lever 24 and permits slight separation of the cup 15 from the sleeve 78. Hence it will be seen that only the downward force of the spring 12 as determined by the adjusted position of the nut 19 on the sleeve 78 determines the pressure at which the switch will be actuated in response to a reduction in pressure.

It will be seen that the pressure values at which the switch may be actuated to operative position are independently adjusted by means of the nuts '19 and 84. While not illustrated, it will be apparent that pointers could be arranged to be moved in accordance with the adjusted positions of these two nuts and that these pointers might be arranged to cooperate with suitable indicia to indicate directly the pressure values at which the switch will be actuated. While the various features of the invention have been illustrated in connection with a pressure responsive device it is evident that any other condition which would produce the same effect as the pressure chamber might be substituted therefor. Also, while the switching device has been assumed to be an electric snap switch, it is evident that any other switching device having similar operating characteristics could be substituted. For example, a control valve operated with a snap action between on and off positions could be employed. Also a mercury switch having an operating angle differential might be actuated in the same manner as the snap switch described. The scope of the invention is to be determined only by the appended claims.

I claim:

1. In a control device, a frame, a member mow able in said frame, a condition responsive element operatively connected to said member and biasing said member in one direction with a force depending on condition value, a switch carried by said frame and operated by said member, said switch being operative to make or break a circuit on movement of said member through a predetermined range, a post secured to said frame, a sleeve slidable on said post, a stop for limiting movement of said sleeve, a first spring having one portion secured to said sleeve and another portion acting on said member, said sleeve also serving as a stop to limit relative movement of the two portions of said first spring, a second spring secured at one portion to said post and having another portion engaging said sleeve and biasing said sleeve against said stop.

2. In a control device, a frame, a member movable in said frame, a condition responsive element operatively connected to said member and biasing said member in one direction with a force depending on condition value, a switch carried by said frame and operated by said member, said switch being operative to make or break a circuit on movement of said member through a predetermined range, a post secured to said frame, a sleeve slidable on said post, a stop for limiting movement of said sleeve, a first spring having one portion secured to said sleeve and another portion acting on said member, said sleeve also serving as a stop to limit relative movement of the two portions of said first spring, a second spring secured at one portion to said post and having another portion engaging said sleeve and biasing said sleeve against said stop, and adjusting means for adjusting the bias applied by said first spring to said member and by said second spring to said sleeve.

BERTIL L. JOHNSON.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,827,084 Henning Oct. 13, 1931 2,028,893 Bondurant Jan. 28, 1936 2,138,509 Raney Nov. 29, 1938 2,150,203 Bondurant Mar. 14, 1939 2,453,861 Rothwell Nov. 16, 1948 2,480,538 Barr Aug. 30, 1949 

